I have almost all the parts for the Zen ready, so I’m looking to dimension the table.

Just to double check before I cut pipe, the footprint in the calculator is the edge to edge space that the entire ZenXY will fit in. So in your sample table which is 36"x60", the no-kidding inner dimension of that cavity is 34.5"x58.5" which are the numbers to use in the calculator (minus perhaps some margin).

I also had this same question and get where John is coming from:

The dimensions of the example table are 36"x60" but this is from outer edge to outer edge. The Zen components will be sitting inside this 36"x60" frame, so you have to subtract the 3/4" wood thickness on each edge and your actual build size would be 34.5"x58.5" (assuming this is correct).